You want to cut nice, neat wedges of that summer pie. The pieces of fruit must nestle cozily and close, thickly bound, and not run off into a soupy puddle. So what do you use?

Ron Silver, who co-wrote "Bubby's Homemade Pies" and has held a pie social with home bakers for the last 10 years, said his thinking on thickeners has evolved.

He started using just flour years ago. But now he prefers something along the lines of a butter and flour roux. "I toss the fruit with flour and then add melted butter," he said. "It's classic and the most flavorful."

With peaches or apricots he might even use brown butter. And with just one exception, he does not like cornstarch as much, even though it acts quickly and turns translucent. In his book, he warns that cornstarch does not thicken well with very acidic fruits. He also finds that the thickening effect of arrowroot does not last as long as that of flour, and the filling can regress to runniness.

"When you have very juicy fruit like raspberries or cherries, instant tapioca is also good," he said. Tapioca turns clear and glossy, does not impart a starchy flavor and adds interesting little gelatinous beads to the texture.

But for a fresh blueberry pie, Silver's favorite, his choice is cornstarch. He cooks half the berries to make a thick sauce with sugar, lemon juice and the starch, which has first been dissolved in cold water. He then folds this mixture into the rest of the raw blueberries to fill a cooked pie shell. He does not bake the pie further, but lets it set for about two hours before serving.

You might get away with no thickener (just sugar and melted butter) especially with denser fruits like figs, stone fruit, apples and pears. But thickened or not, Silver says it's important to wait two to three hours before cutting into the pie, allowing the filling time to settle so the juices released by the oven's heat are reabsorbed.